It is recognized that the repair of superalloy materials is made difficult due to their susceptibility to weld solidification cracking and strain age cracking. The term “superalloy” is used herein as it is commonly used in the art; i.e., a highly corrosion and oxidation resistant alloy that exhibits excellent mechanical strength and resistance to creep at high temperatures. (http://en.wikipedia.org/wiki/Superalloy) Superalloys typically include a high nickel or cobalt content. Examples of superalloys include alloys sold under the trademarks and brand names Hastelloy, Inconel alloys (e.g. IN 738, IN 792, IN 939), Rene alloys (e.g. Rene N5, Rene 80, Rene 142), Haynes alloys, Mar M, CM 247, CM 247 LC, C263, 718, X-750, ECY 768, 282, X45, PWA 1483 and CMSX (e.g. CMSX-4) single crystal alloys.
Brazing processes are used to repair superalloy materials in some applications. While a braze joint is generally understood to be mechanically weaker than a weld joint and to have a lower acceptable operating temperature due to the relatively low melting temperature of the braze material, braze repairs may be acceptable in certain lower stress and/or lower temperature applications.
Typical braze materials using boron or silicon as the melting point depressant material are of limited value with superalloy substrate materials because they create deleterious phases which reduce the ductility of the joint and repaired region. Boron and silicon free braze alloys incorporating hafnium and/or zirconium have been developed for which mechanical properties of up to 80% of the base superalloy properties are claimed. However, such materials tend to form carbides at the braze joint. Thus, further improvements in the brazing of superalloy materials are desired.